Economic power generation assignment devices



Sept. 26, 1961 J. l.. MGKINLEYv ET AL 3,001,714

ECONOMIC POWER GENERATION ASSIGNMENT DEVICES 3 Sheets-Sheet 1 Filed Deo.

w Q Nm.

Sept. 26, 1961 Filed Deo. 19, 1956 J. MOKINLEY ET A1.

ECONOMIC POWER GENERATION ASSIGNMENT DEVICES 5 Sheets-Sheet .2

SHIFT suMMAnoN AMPLIFIER +`WHEN INCREASING WHEN DECREAS|NG I 34"@ 1 ii ;A*`3| FIG/2 SOURCE 60 N AC 5 Sheets-Sheet 3 J. L. MCKINLEY ETAL ECONOMIC POWER GENERATION ASSIGNMENT DEVICES Sept. 26, 1961 Filed Dec. 19. 195e 3,001,714 ECONOMIC POWER GENERATION ASSIGNMENT DEVICES t John L. McKinley, 660 Oneida and DaleO. Ballinger,

1690 Lewis, both of Denver, Colo.

Filed Dec. 19, 1956, Ser. No. 629,404 19 Claims. (Cl. 23S-e184) This invention relates to a method and apparatus for calculating and `automatically allocating the most eco- Vnomic power generation assignment among any number of electric generators operating togetherv on a power system in accordance with facts usually known or immediately available during the course of normally'acceptedprocedures for operating any power system having more lthan one power generating unit; more specifically, it provides in one compact unit a calculator embodying electronic equipment for accurately lacconiplishing theseV purposes which are more generally known ybythe technic'al terms, economic loading or incremental loading; since the lowest cost of production-of --power usually results when the next increment ofsystem load is added on the generator having the lowest incremental cost and conversely when the next decrement'of -system load is taken away from the rgenerator operating at the highest decremental cost..

Usually, a loading pattern for. a power system is developed from a group of curves orvnumerical tables which serve as a guide lfor the power system operators infmaking the load assignments on generators lwhich will provide the lowest overall cost of generation. .'Basically, inthe case of fuel operated generating units the. performance for each generating unit Vis represented by an inputoutput curve, where the input is usually evaluated in British thermal units heat input per hour and the .outputrepresents kilowatts generated. The. input might be evaluated in the equivalent of heat as units offuel or aslacost .per unit of -heat -or of fuel. Since an input-output curve represents the overall eiciency of thesource of energy, its conversion into useable mechanicalenergyand finally into .electrical energy as the end product, it is evident thatV it is an accurate means for determining relative costs of production. The most common, but not limited, ap plication is the one steamboiler and one turbo-generator power generating unit of the modern power stations. If tbe heat input and the power generated are plotted on an input-output curve for the specific generating unit, the slope of the curve at any output or kilowatt load repref sents'the incremental heat rate at that load. Since the graph is a continuously curving line the slope is different at any point and a -very largenumber of incremental heat rates can be obtained; more than it is practical to recognize. However, if the curve is divided into any number of equal segments each represented by a straight line, the curve becomes a series of straight line segments each of which will represent a const-antincrementalheat rate. :If the number of segments is properly chosen, no

`significant sacrifice lof accuracy will result. vThe heat rate curves are so represented in this device as will be explained in detail.

However, heat rate or input-'output curves are .subject to many variables -all of which must be recognized if reasonable accuracy is to result from the automatic comparison-and selection of economic incrementalload assigne;

ments.l A given boiler and turbo-generator unit operat-f'V ingunder optimum conditions will obtain a given heatv rate but if any of the conditions are changed the heatv rate also will be changed. A diderent combination off boiler and turbo-generator will usually result in a different'4 heat rate and the operation of a turbo-generator from a steam header supplied by two or more boilers will pro?" duce variations-in the heat rate depending upon the'- -An imicombination of boilers in service at lany time. A portant factor which inuences the heat rate is the turbine' back pressure or vacuum which varies with the con`` densing water temperature and condition of the condenser which are both variable. However, a convenientiv index to fthese variables -is instantly available from th-l vacuurn gage readings and with this information the aplpropriate alteration in the heat rate curve can be made'- in this device to reflect the change and condition at any. In any of the similar devices heretoforedevisedj provision has not been made for correction of the heat rate curve by the direct insertion into the computation?! time.

of vacuum, per se, as usually measured and as available instantly at any time in inches of mercury.

The cost of fuel and kind offuel are factors to use a factorl common to allrtypes or combinationsof' fuels. t In this device fuel is evaluated in. centspermilfl lion British thermal units which is a known and instantlyavailable value; therefore, the lkind or proportion of combinations of fuels used at any time only need. be known and the corresponding appropriate cost of fuel irr cents per million B.t.u. as predetermined for each genen.. ating unit will be inserted directly into the computation.' Since load assignments on interconnected generating stations and frequently within a station are not always' made on .an economic basis due to necessities such as optimum minimum loads, required boiler loads for slagging, bled steam requirements, etc., provision must be made in computation for handling these special situa' tions conveniently without sacrificing thcuaccuracy of the computations affecting other generating units on the power system. In this ,device the provision for locking these special load assignments into the overall load requirement of the system is more easily accomplished and is visually more evident for each generating unit to which such special assignments are made than in anysimilar device heretofore devised. i

Similarly, maximum and minimum load assignments for any generating unit are known from test data and; experience and are subject to variations as affected by conditions known to exist at any time. Provision .in this device-for visual observation of these load settingsA is augmented by the illuminated warning signals show-'- ing that theA maximum 0r minimum load asY displayed iras been attained; thereby giving notice to the operatorof the exact assignment of loads among the generators on the system as related to the maximums or minimums established at any time on individual generating units.

In operating a power system it is essential in the interest of continuity of service Ito its customers that reasonable precautions be taken to insure against the unforeseen and probable failure of any part of the system;

Usually, it is the practice `to operate generating capability,

Patenten sept. 26,1961

which'. enter into the determination ofA economics and `produc-1- tion costs.` Rather than to provide for the selection ofI spinningjandfcionneeted to the system, in excess of the expected maximum load on the system and the excess of capability over system load to be made instantly available is usually established at least equivalent to the largest generating unit or other source ofpovver on ythe system that might thru some unforeseen circumstance fail. No othersimilar device heretofore devised has automatically provided for the direct computation and visual observation of spinning reserve instantly under `any condition of system loading or availability of power sources.

The incremental cost of electric energy generated by any .combination of generating sources and under anyl ,conditions Yis instantly available iand mayI be observed computation of the, so named, penalty factors relating i to transmission losses; however, it provides for the in-f sertion of generator assignments as modified by trans mission losses as determined by' analysis, digital cornputation brother fvmethod. It also provides for the iusertion into total load of other sources of power not inuenced by the incremental cost of energy produced onthe systemfor whichthe device is designed. t l

: Zine object of this invention is arelatively low cost analog `computer for thev instantaneous determinationy .of

incremental costs of generating electric energy'from data readily available during the courseV of normal operations ofa power system.

A further objectl ofthis. invention is, to prtwide` a device for independently checking andvalidating the operation ofv automatic power system load control equipment. y used on an electric powervsystemV to change generator 'load assignments in accordancekr with predetermined schedules, usually made on a percentage change vs. perccntage load basis, which schedules are not .subject to the modifications and effect of instantaneous changes-in oper-l ating conditions as available from this invention.

A'further object of this .invention is to provide a device for ,the calculation of the economies likely to result from the selection of additional new generating units to be installed on an electric power system.

further object of this invention is to provide acalculationv for determiningthe eect of inavailable generating units on a power system so that the' economies associated with shutidown time can be-readily evaluated, eg., economic `justilication for accelerated maintenance schedules.

A further object of this invention is to provide a calculator for determining instantaneously under any schedule or optimum operating conditions the quantitative evalua- Y tion of spinning reserve on an electric power system.

A furtherA object of this invention is to provide instantaneous quantitative and visualV indication of the type of t generation assignment resulting on any generating unit onl the power system under any given conditions. f

'Atfurther object ofrthis invention relates to the convenience of having in one relatively small space -all of the essential devices for the determinations and evaluations herein recited and to the portability of this device. .1A further object of this invention relates to the convenience andflexibility .afforded thru the design permit? tngitheuse of plug-in typev variable quantities so that components are interchangeable' and so that an inita'l computer may be expandedk as additional generating units are Yaddedon the/power system by theaddition of'one p t f comme bility toA any power system where more than one generating unit is in service.

With these primary and other essential objectives in View, as will be more fully developed in the spcciication, this invention consists of the electrical and mechanical feature-s of construction, electronic circuits, the parts and combinations thereof and the mode of operation or the equivalent as hereinafter described and set forth in the v claims.

i purposes ofthisinvention.V

- power system dispatches computed by this invention. l

Like parts are indicated by'similar characters of reference thruout lthese views. y i

Each generator on the power'system, is represented by. a device. as illustrated in FIGURE .1'. v,The operation of this. device is'as follows:

The conduction thru the Thyratron tubel 'il is conf.

-trolled by they `coml'ination of voltages at points l2, 13

and 14. The voltage 4atgpointvlZ isproportional tothe incrementalcost of generated power. This voltage is l positive (--l when the cost is increasing` andv negative thermal units and by calibrationk the fuel cost dial may,-

standard plug-in type lpanel representing the .added genwhen the costis decreasing..v The voltage at point" 13 is proportional tothe fuel cost.` The voltage at point Y14 is, proportional to ytliernininunn. generation setting if, the incremental cost is increasing and to the maximum generation setting if .the incremental cost is decreasing.

thus, conduction thru the Thyratron tube '11 is; a Vfunction of the fuel cost of the generator, the maximum or mumlsetting ofthe generation .for the generator and the incremental. cost of generated power common to all gen-A oratore.

The' fuel cost rotaryiswitch 15 for each generator is adjusted `for the cost of fuel being iired for operatingk the generator. By appropriate choice of electricalcircuit constants the electrical resistance. controlled by switch 15 yrepresents fuel cost .in cents per "million Brltlsh he 'made to read directly in centsper million Britishtherrnal units. n

The minimum generation adjustment rotary switch 16 is adjusted similarlyv proportional to the desired minimum generation for each generator andthe dialassociated- With switch 16 maybe calibrated to read in kilowat'ts or megawatts.

'The maximumgeneration adjustment rotary switch 17 is `adjusted similarly proportional to the desired maximum generation for each generator and the dial associated with switch 17 may be calibrated to read in kilowatts or megawatts.

The Thyratron tube 11 will now conduct at a predetermined incremental cost of generation as lindicated by the voltage at point 12 which is obtained by the precise linear potentiometer 18, FIGURE 2. This poteutiometer'lS is electrically operated tin equal steps by the rotary solenoid actuated Steppersv 19 and 20 controlled 'by push buttonsV Z5 and' 26.'

Stepper 19 operates potentiometer 18 in avdirection to increase the positive voltage at point 12 land stepper 20V operates potentiometer- 18 in a direction to decrease the negative (f) voltage at point 12p; thus,'the Thyra-4 tion tube 11 can be controlled to conduct when the iucremental cost is either increasing or decreasing. a Whenever the Thyratron tube 111conducts the latch relay 22 operates. This relay 22 :electrically connects the 'generator .rotary switch. actuating solenoids'v 2.3. and -24 to anormal the increase .push button z5, FIGUREv 2, and m the' decrease push button 26, FIGURE 2. The push buttons 25 and 26 then operate they generator rotary switch as well as the incremental cost potentiometer 18.

The generator rotary switch has three rotary sections: 'lher function ofthe .tirst section 27 is to release relay 22 when' the generator setting has attained its-maximum or point. The second section 28 prevents the Thyratron tube 11 from conducting and consequently prevents relay 22 from operating when the generation has reached maximum when increasing vor minimum when decreasing. The third section 29 is the electrical equivalent ofthe incremental heat rate curve for a speciiic generating unit on the power ysystembroken into a number of straight line sections represented by appropriate electrical resistances; therefore, this section obtains a voltage which is proportional tothe incremental heat rate Afor the generator.' 'Ihis voltage isY appliedto the summation amplier 30 along with the various outputs from other similar generator sections and along with other system voutputs represented by variable resistances 40 not entering into the economic dispatch computation brought together Iat point 42. These are all summed and the total system generation or total system load is displayed on meter 3.1. The individual generation ofutptits' which make fup this total'will be displayed separately on individual meters 32. 'Phepanel light 33"indicates visually when the genenatoris operatingin its regulating range;that is, it is operating somewhere between its maximum and minimum values. Similarly, panel light 36Vindicates visually when the generator is operatinghat its assigned minimum value; Similarly, panel light 37 indicates visually when the generator is operating lat its assigned maximum value. Meter l34 indicates the voltrage at point 12 and is calibrated to display the incremen- .tal cost of delivered power on the system in mills per kilowatt hour, since this voltage is proportional to the incremental cost of `delivered power. h ,'If it is desired to sethinto thecomputation a fixed generation value on any generator the potentiometer 12% is temporarily adjusted by the push buttons 25 andl26 the desired fixed generation is displayed on meter 32 for'the speciiic generator for rwhich. the fixed load assignment is required and at this point switch B9 is :opened thereby releasing relay 22 which prevents the generator sections as controlled Iby steppers 23 and 24 from-participating in adjustment to the total power system load' until switch 39 is again closed, thus, the speciiic generator unit required to accept` a xed load assignment will not affect the accuracy of the properV distribution of load among the other generator units simulating the power system not operating on a' iixed assignment.

i Variable resistances vor potentiomete-rs 38 are inserted :into the circuit to adjust the position of the fuel cost rotary switchin the circuit. r[wo such devices precisely connected are necessary; one obtains the correct position of vany speci'c generator on the incremental cost axis of lthev incremental heat rate curves which incremental cost axis is represented by the uniformly variable voltage at point 12 common to all generatorunts on the system; the other device will accomplish the same effect in relation to predetermined corrections necessary 'for the turbine back pressures; however, inthis instance it is necessary to calibrate the dial to readin absoluteV inches of mercury back pressure, a value readily obtainable from the normal complement ofinstruments associated with turbo-generators on a power system.

-The variable resistance 29 representing the electrical equivalent of the incremental heat rate curve for a specific generating unit on the power system may be Vmodi'ed by transmission lossY penalty factors computed by any conventional method and the so modified increvmental heat rate curve may be substituted for, any other -six'nilarly modified incremental heat rate curve or for an iiD incremental heat ratel curve not so modifiedby simple' substitution of the electrical resistances represented Vby.` 19. This may be accomplished by electrical switching or other means; such as, plug-in type resistance If the total generation assignment as computed by this device for any condition is subtracted from the summa-l tion of the maximum capabilities of al1 of the generators on the system entering into the computation the remainder is the spinning reserve or the reserve of ava-ilable power in excess of power system load requirements at the time. By depressing the spinning reserve push button 35 the maximum capabilities of all generating units are impressed on the summation ampliiier 30 after being shifted in phase 180." by the phase shifter 41`so that the output-as displayed on meter 31 is proportionalV to the spinning reserve and since meter 31 is calibrated in kilowatts or megawatts a direct reading of this value is obtained.

Thus, this electrical circuit is capable of reproducing,

in straight line steps, thev incremental heat rate curveofa power system generator and if each generator on a power system is represented by such a circuit the most economical operating point of each generator on the power system can be obtained for any total load on the power system. s

It is assumed, for sake of simplicity, that the `power system includes three generating units on which itis desired to determine the economic assignment of respective generations by means of the invention under the several conditions to be related. Each of the three generators is represented bya device as illustrated in FIGURE lof the application. It is assumed that the appropriate electrical resistors have been inserted into the circuit to represent the incremental heat rate of each generating unit', the maximum generation settings, the minimum genera.- tion settings and the fuel cost; also that the required c orrection of positioning ofthe fuel cost adjustable resistance in theV circuit has been predetermined so that the changes in turbine operating eiciency or economy (back pressure) can b e compensated for in relation to thecost of generation. Having thus prepared 'the electrical equivalents of each generating unit Aeach as represented by a de. vice similar to FIGURE l of ,the application andhaving made theV appropriate electrical connections to a control device FIGURE 2 of the application reference is now madeto the graph of FIGURE 3:.v

The three generators assumed for illustration are designated respectively:

Unit No. l--lO mw.-Capability 115 mw.

Unit No. 2-66 mw.-Capability 70 mw.

Unit No. 3--44 mw.-Capabi1ity 47 mw.

The total capability is 232 mw.

The incremental heat rates for each of the generating` units are plotted as shown: Gross generation vs. incremental cost per net kw. h. generated Iin mills. The abscissa thus represents incremental B.t.u. per net kw. h, generated evaluated in equal increments ofcost the analog vof which ist-a voltage controlled in equal increments by the precise linear incremental cost potentiometer 18, FIG- URE 2. This potentiometer, in fact, isrthe abscissa of the plot shown representing the voltage .at point l12, FIG.- URE 1 which is positive (i) When the cost is increasing and negative when the cost is decreasing from a source of direct current supplied to potentiometer '18, FIGURE 2, which change in polarity can be accomplished by various well known means suc-h as a manual throwover switch, a relay or other common device actuated .in conjunction with the push buttons 25 and 26. The circuit conditions detailed on FIGURE l are similarly aecomplished as push buttons 25 and 26 are operated to increase or decrease the control voltage in equal increments representing equal steps of cost and in turn the desired power system total generation requirement as displayed on meter 31 appropriately calibrated to read in megawatts selected 'for' the example.

systemA powerrequiramentfas Veach generating unit is vlzrlaugltt:intothe circuits.

Referring to angepat- FtGuR-n 3., each of thethree A tiouing the generation rotary switch 16 and j' thefmaximum generation rotary switch 17 appropriat for each generating unit. Y

' ProblemNo'. 1.,--Assume that the three generating units are operating availableto accept power system load and thatthe costs. of fuel required to operate each unit are equal; Ialso .that theunits .are operating with normal tur- Y bine back pressures.

lIt is desired that no special minimum or maximum load setting limit the generation onany uni-t--that is, onlythe first minimum step andlast maximum step will be `set on rotary switches 16 and 17 for each unit. It is desired to compute the correct economic generation assignment for each generating unit for -a system load of 165 mw.

`Push buttons 25 :and 26 are operated to adjust the control voltage step by step until meter 31 displays 165 mw. At this point the Vseparatemeter 31,V FlGUREl, on each generating unit device will display the correcti generation assignment for that unit. `Unit No. 1 should be generating 86'mw., Unit No.V 2 should be generating'SS mw., and Unit No. 3 should be generating 24 mw. The sum of these generation assignments is 165 mw. which solves the problem. The vthree generating units arey operating at Y equal incremental cost which is displayed on meter 34 and Y todetermine the spinning reserve available pushbutton 35 isdepressedto display on meter 31 the summation of ythe maximum capabilities of the three generating units shifted in Vphase 180' 'by lphase shifter 411 therefore representing vthe remainder (232 mw; capability less 165 mw. assignment for system load). shown on the graph as 67 mw. spinning'reserve.

' Problem N0. 2.-]Assume that the general' conditions set forth underproblem No. l are valid. It is desired that the correct generation assignments among the three gen erators be determined for a system load of 194 mw.

` Bush button 25 is `depressed to' operate stepper-13 in the directionto increase the control voltage until 194 mw. is displayed onmeter 3'1 which in` this example represents un vincrease in cost from 2.225 mills to 2.3 mills per net kw. h. displayed on meter 34 and as indicated (ordinate B) on the graph atwhich point the correct generation as- -signmentsread on'the respective meters -32 are Unit No. l, l100 mw.,` Unit No.A 2, 62 mw. and Unit No. 3, 32 mw.

lThe/spinning reserve similarly becomes 38'mw. las read -by depressing push button 35. Y

Problem No. .if-*Assume that the general conditions -set forth under problem No. 2 are valid except it is desired -tthatN'ol lunit shall belimited to a maximum generation fof 90r'nw. The-maximum generation rotary switch 17 of 1194 inw. is displayedoumeter 3.1. The respective gen eration vassignnuents vread on meters'32 are Unit No. `l, .90,1mw'., Unit No.2, 65 Inu/.and UnitNo. A3, 39 mvv. As .before thespinning reserve is 38 mw. The control volt- `ageeas .measured in mills per net lkw. h. has advanced from 2.3 mills per net hw. hrto 2.375 mills per net kw. h. as shown onmeterc#andby'ordinate andline C on the stephnerease in eostof. generation obviously re resents the penalty for transfer-ling to Units No .t the 1,0 mw. of generation which eouldmore economically. be generated on UnitN'o. 14 had it not been to 90mm maximum-, Problem No. v4.f-.-Assume that. the general e conditions. Set forth under problem N0.- 3 are valid except it `is desired. to reeet in the economie. .dispatch the eiect of au linierease in fuel cost 0r an equivalent change in. turbine hack Pressure equal to four Vfuel @est steps. VEither thefuel.. cost rotary switch `145 ofthe device representing Unit. No, 3v is advanced four steps in eQStifthe occasion is wholly a fuel cost increase on Unit No. 3 or potentiometer 3 'is adjustedthe equivalent offour lsteps in costas calibrated if the occasion iswholly due to a change in turbine etliciency as conveniently available from the ;turbine back pressure. Obviously, similar adjustments of. any meg# nitude in consonance with the operating conditions of any generating unit may be made simultaneously.v

In this example the increase of four yfuel cost steps for Unit No, 3 will have the reffect of shifting Ithe incremental fheat, rate curvey to the Vposition shown .dotted pn the graph -four cost steps advanced each step equivalent to $0.0().0025 per net kw. h. '.I'hereforegthe` computation so played onmeter 31 `as before by depressing push button 25 to operate stepper 19 to increase the control voltage,

'Illegeneration :assignments are UnitrNo. 1, 9,() mw., Unit No. 2, 70 mw. and Unit No. 3, 34r`nw.- T hespnning reserve is 3,8 mw. The incremental costof genera.- tion as shown on the graph and as displayedA on meter '351 is`2.4,5.mills per net kw. h. represented .by ordinate and line D.V v

The penalty for having to reassign generation. due to the four cost steps increase in cost of generation on Unit No. 3 asshown isequivalent to 2.45 mills less 2.375 mills or 50.010007 5 per net kw. h. occasioned bythe transfer of .5 mw. of generation fromUnit No. 3` to Unit No.2.

Problem No. 5 (notshown on the graph)..-Assume `the `saine general conditions as set yforth under problem No. 4

are valid withA thev .exception that UnitNo. `2 will not be Y permittedto generate more than mw. Since 65 mw.

is not a predetermined maximum set pointit is necessary to position potentiometer 18 by `depressing push button k25 or 26 to operate Steppers 19 and 20uuntil 65 mw. is dis,.- played on Unit No.2 meter 32 at which point switch 39,

is opened'to release relay. 22 vso that the Unit No. 23enerator device. will not participate in yfurther system v assignment. p

-Since the required system load is `194 mw. push button v25 will be depressed until stepper 19 haspositioneddpo'- tentiorneterV 18 so that 194 mvv. lis displayed on meter 31.

Y Evidently Unit No. 1 cannot participate in an inereSC in HSystem requirement kgreater than mw. since the maxii mum generation on this unit has been so-fsetY land Unit No. 2v cannot now participate in an increase in system requirement greater than 65 mw., sincev this generation has been iixedat 65 mw. The system requirement `must Y be satislied by Unit No. 3 the generation assignment. for which will ,be displayed on meter 31. The increased cost of. transferring 5 mw. of generation from Unit Nc- .2 to Unit No. 3 by reason VVof lixing a limit of 6,5 mw. participa,-

` tionvon Unit No. 2 is, rreading from the graph, at39 v1n-w.

on the shifted Unit No. 3 Yheat rate curve 2.4757mi11s less 2.450 or 350.00025 per net kw. h. Meter 3,1 will display Vinvention it is neceSsa-:rytoy suggest that theprecedingproblems are *only illustrativeof the most usual computation.' Obviously as push buttons 25 and 26 are depressed to operate steppers 19 and 20 to position the precise linear potentiometer l18 and as the auxiliary switches or relays associated with the operation of push buttons 25 and 26 will change the circuit as shown on FIGURE 1 and the input voltage to potentiometer 18 Veither to positive or negative as the direction of rotation of themovable arm of the potentiometer is changed either to increase voltage or decrease voltage as vrequired the voltage delivered at point 12, FIGURE 1, will become positive when increasing and nega-tive when decreasing. Such voltages are proportional to the incremental costl of generation of power as has been described in the problems.

The voltage at `point 13, FIGURE l is proportional to the fuel cost as has been describedin the specification and as shown in FIGURE l.

The voltage at point 14, FIGURE 1, is proportional to the generation setting if the incremental cost is increasing :and to the maximum generation setting if the incremental cost is decreasing. Since the voltage at point 12 Vcan be controlled as has been described to increase' positive or decrease negative the Thyratron tube 1t1 can be controlled to conduct when the incremental cost (control voltage) is either increasing or decreasing. The Thyratron tube 11 must conduct at a different incremental cost or control voltage when the generation is increasing than when .the generation is decreasing; therefore, the voltagechange at point 14 is proportional to the minimum and maximum generation setvrings. Assuming that the incremental cost (control voltage) is increasing it is desired that the Thyratron tube 11 shall conduct at the lowest point of the incremental heat rate curve to operate relay 22 so as to cause stepper 24 to operate the generator rotary switch, section 29 of which represents the electrical equivalent of the incremental heat rate curve. Stepper 24 will operate then as push button 25 is depressed yand all devices of FIGURE l -will operate together in step under the same conditions whenever push button 25 is depressed. As the incremental cost (control voltage) is increased by continuing to depress push button 25 stepper 2.4 continues to operate rotary switch section 29 until a maximum is reached at which point relay 22 releases and nourther increase is indicated forthe generator so represented even though the incremental cost (control voltage) continues to increase beyond the set maximum value Afor the generating unit represented.

Similarly as the incremental cost (control voltage) is decreased by depressing push button 26, stepper 23 will operate to change the position of its associatedrotary switches including rotary switch section 29 provided that the 'Ihyratron tube 11 has conducted to operate latch relay 22 thereby lconnecting stepper 23 into the circuit. As the incremental costV (control voltage) decreases Thyratron tube 11 will conduct -when the set maximum generation is reached thereby operating latch relay 22 and connecting stepper 23 into the circuit until the set minimum generation is reached at which point latch relay 22 will release and no further decrease in generation is indicated for the generating unit represented even though the incremental cost (control voltage) continues to decrease beyond the set value for the generating unit represented.

It has been illustrated by means of the problems that several generating units are represented by appropriate incremental heat rate curves may be positioned on a voltage axis represented by uniform incremental costs, the abscissa of the graph. The positioning of these separate heat rate curves on the voltage axis is predetermined for similar conditions of operation vof `each generating unit represented. It is desired to build into this device means for departing from said similar conditions by making adjustments as required by operating conditions. These conmens may' be recognized as desired' ha mmum and i' mum values of generation, required changes in fuel costss and necessary adjustments in economy due to turbine back pressure changes. All of these adjustments as has'` been demonstrated in the problems will cause changes in the points (voltages) at which the Thyratron tube 11 willi conduct. Referring to the rotary switch 27 of FIGURE 1, it" evident that four contacts on this switch near the upper'l limit of travel are connected to switch 17 which lis the maximum generation adjustment rotary switch, the movable arm or contact of which isv always grounded whenl the generation is increasing. A ground thru this movable arm or contact can be placed on any of the four upper oon-- tacts of rotary switch 27 as selected by switch 17. Wherr. rotary switch 27 has increased to the selected contact representing the desired maximum generation as referred' to switch 17 the latch release solenoid of relay 22is energized. This release of relay 22 removes the ground fronn rotaryvswitch 27 by opening the fourth group of contacts) of relay 22 and causes stepper 24 to operate thru thel third group of contacts of relay 22 to ground. Rotary switch 27 will never make a complete revolution since'I conduction thru its movable arm or contact -is limited both in an increasing direction and in a decreasing di,- rection.

Similarly, the minimum generation assignment is ace, com-plished thru the four contacts on rotary switch 27' near the' lower limi-t of travel which are connectedv to switch'16 which is the minimum generation adjustment rotary switch the movable arm or contact of which is always grounded when the generation is decreasing. A ground thru this movable arm or contact can be placed on any of the four lower contacts of rotary switch 27 as selected by switch 16 causing the same operations result@ ing from the energizing of the release solenoid of relay 22 as just described. Switch 16 will be set on the contact' representing the desire-d minimum generation.

While ta specific yform of the improvement has been described and illustrated herein, it is to be understood that the same may be varied within the scope of cheappended claims, without departing from the spirit ofthe invention.

Having thus described the invention, what is claimedy and desired secured by Letters Patent is:

l. Means for allocating the most economic power gen1 eration assignment among a plurality of electric generators comprising in connection with each generator the combination of a thyratron tube having a cathode, a grid and an anode; a vfirst means supplying current to the grid of said tube at va voltage which is proportional to the incremental cost of the power being generated by the generator; a second means supplying current to the grid of said tube at a voltage whichis proportional to the cost of the fuel being used by said generator, so that the total voltage supplied to said grid will be proportional to the incremental cost of the generated power; a third means supplwng current to the cathode of said tube at a voltage proportional to the minimum generating setting if the incremental cost is increasing and proportional to the maximum generating setting if the incremental cost is decreasing so that current conduction tothe anode of said tube will be a function of the fuel cost of the generator, and a variable resistance fuel cost adjusting device in circuit with the second means for supplying current to the grid of saidtube, said resistance being calibrated in cost per B.t.u.s.

2. Means for l.allocating the most economic power generation assignment among a plurality of electric generators as described in claim 1 having a variable resistance minimum generation adjusting device which may be placed in circuit with the third means supplying current to the cathode of said tube which may be manually adsoort-ra 1L instel to .the desired generation of Said soh- 3'Means for allocating the most economic power genera-tion assignment among a plurality of electric gen-t' circuit in saidthird means whereby either' said minimum generation adjusting device or said maximum generation adjusting device may be placed in the circuit of said cathode- Y Means vfor allocating the most economic power generation assignment among a plurality of electric generators as described in claim 4 havingga rotary potentiometer in series with said first means supplying current to the grid oi said tube `for adjusting the current in proportion to the incremental cost of generation. Y

t 6. Means for allocating the most economic power generationassignmentf among a plurality of electric generators as described in claim 5 in which the potentiometer is connected between a positive and a negative current supply .so that when rotated in one rdirection it will increase'the positive voltage supplied to said kgrid and when rotated in the other direction will increase .the negative voltage supplied to said grid so that the thyratron tube can be controlled to conduct when the incremental costs are either increasing or decreasing.

'7'. 'Means for allocating the most economic power generation assignment among a plurality ofyvelectric generators as described in claim 6 in which the two-,throw switch comprises: a first rotaryswitch which during s ubstantially 180i' of its rotation willconnect rsaid minimum generation adjusting devicev in circuit with said cathode Vand dungthe remaining substantially 180 will` connect said maximum'generaton adjusting device in saidk latter circuit; a multipole latching relay in series with the anode of said tube; means dior yunlatching said relay; and a second rotary switchconnected to revolve synchronously withsaid [first rotary switch to prevent said tube from conducting when generation' has reached maxim-um when increasing and minimum when decreasing; lnld a 'Iirst solenoid for rotating said rotary switchesin one direction and a, second solenoid -for rotating said yrotary switches in the opposite direction.

8. Means for allocatingthe most economic kpower generation assignmentr among a plurality of electric generators asf described in` claim 7 having a variable resistanceincremental heat, rate curve mechanically connected with the rst rotaryswitch so that the two will be si.` multaneously actuated by said` solenoids; and said variable resistance incremental heat rate curve is connected in vSeries with a source of power sothat said variable resistance incremental heat. rate cuive varies the, volti afge in directy relation to the quantity lof resistance vin the circuit at any given time, which voltage represents the most economic power 'generation assignment atany given time.

` 9. Means 'for allocating the most economic power gen leration' Vassignment among a plurality of electric `generators -as described in claim Shaving the electromagnet of said multipol'e relay in series with the anode of` said tube;

l2 rotary switgh so as to rotatetherewith and in which said second ,lQtry switch is connected to said unlatching meanr in said multipole relay to release the latter when the generator setting has reached its maximum or minimum point.

l1. Meansv for allocating the `most economic power generation assigrnnent4 among a plurality of electrid genators as described in claim 3 having a two-throw switch in Y able resistance incremental heat rate Curve to odd. 'the erators as described in claim 10 having said first rotaryv switch, said variable resistance incremental heat rate curve and said second rotary switch mechanically interconnected and operated by said solenoids controlled by said multipole relay, said thyratron tube and said maximum and minirnum'rotary adjustingdevices all of which are actuated by said potentiometer controlling the supply of current` to the grid of said tubeandmanually operated two-throw switch fork actuating the third solenoid for rotating said potentiometer arm in one direction and a`V fourth solenoid for rotating said potentiometer arm in the opposite direction so that said rst solenoid and said third solenoid shall operate simultaneously and said second solenoid and said fourth solenoid shall operate simultaneously when permitted to do so by the combined: interaction of said potentiometer, said thyratron tube, said inultipole relay, said maximum rotaryadjusting devise and said minimum rotary Iadjusting device. t

l2. Means for allocatingthe most economic power generation assignment among' a plurality of electric generators as described in claim 1l having a first voltrneterf calibrated to -read in mills per kilowatt-,hour connected in the electric circuit with said potentiometer to measureincremental. costl of: generatedpower. t

1.3. Means for allocating the most economic power generation assignment; among a plurality of electric gene tors as described. in claim 12 having a second voltnY calibrated, to, read. in megawattsy or kilowatts conllecle. the electric circuitxwith each. said variablev resistance generation. assignment among a plurality of electric se 'Y erotorsas deseribedin claim 13 having a summation pliierconnected in the electric .Circuit with each said.

separate quantitiesy of generated power` allocated to cash electric generator represented by voltages and to. aus@ Said: to-be measured by a third voltmetor calibrated to read-in meaawatts or kilowolits representing the total seneratedpower: Y

15- Means 4for allooatingthe most eooaomiopower. gere eration aissianoioot among a plurality of electric sonorators as described in Claim Y14 having o 180 Phaseh er connected. in the electric circuit withl said variable. resrstf ancein remetal heat rate, curve, said summation tier, saidthird v oltrnoter and. a one Polo Switch yfor. .ae'tuf ating Said Phase Shifterv vS0 that Said sum oi gener-ated power, allocated will be subtracted by ,SaidA Phase Sh' er from, .the total available generated power the .remainder ofvwhichiisv displayed on saidthird voltrneter as available spinning-reserveeleetricpower.4V t Y v 1.6. Means for allocatingthe most economic power generation assignmentamongaplurality of. electric gen;-V i crators as described inclaim 1'5 having a one-pole switch` connected in theclectric circuit with the unlatchingrneansr ofjsaid'multipole relay so that at any point representing a desired `generated -power allocation said one-pole switch'I Y may be opened to opcrate the unlatching means or' said"y mu'ltipole relay thereby establishing the desired invariable allocation ofpower' generation.

` 17,':Means for allocatingthernojstV economic power generation assignment among a plurality of electric generators as describedinV claim 16 having a manuallyoperated'irst dual potentiometer connected in the electric cirj- Y 13 spect to the variable voltages impressed on the grid of said thyratron tube for purposes of calibration.

:18. Means for allocating the most economic power generati-on assignment among a plurality of electric generators as described in claim 17 having a manually operated second dual potentiometer calibrated to read inV absolute inches of mercury back pressure connected in the electric circuit with said'variable resistance fuel cost adjusting device to position said variable resistance fuel cost adjusting device in the electric circuit appropriately with respect to the computed positioning of said variable resistance fuel cost adjusting device required to reflect the eiectrof the variations in turbine back pressures from normal.

14 19. Means for allocating the most economic power generation assignment among a plurality of electric generators as described in claim 18 providing for the direct substitution for said variable resistance incremental heat rate curve by any appropriate commonly used practice with a modified similar variable resistance incrementall heat rate curve representing the required modifications of said variable resistance incremental heat rate curve for transmission loss penalty factors.

References Cited in the iile of this patent UNITED STATES PATENTS 2,508,538 Posthumus May 23, 1950 

